A computer model for the gel effect in free-radical polymerization

Chiu, Wen‐Yen; Carratt, G. M.; Soong, David S.

doi:10.1021/ma00237a002

Cited by 263 publications

(260 citation statements)

References 6 publications

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“…Como no caso anterior, estes fenômenos conduzem ao alargamento da distribuição de massas molares e afetam fortemente as propriedades finais dos polímeros [35,53,54] . O efeito vítreo aparece em polimerizações em que a temperatura de reação se encontra abaixo da temperatura de transição vítrea do polímero, em conversões superiores a 90%.…”

Section: Efeitos Gel E Vítreounclassified

Uma revisão sobre os processos de polimerização em suspensão

2007

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Resumo: Inúmeros processos podem ser utilizados para produção de materiais poliméricos. Cada processo apresenta características peculiares, que permitem produzir resinas com as mais variadas propriedades, visando a diferentes aplicações do material polimérico final. Os processos de polimerização em suspensão são bastante empregados para produção de resinas poliméricas por apresentarem muitas vantagens, como a facilidade de separação, fácil remoção de calor e controle de temperatura e, principalmente, pelos baixos níveis de impureza e de aditivação no produto final. Por isso, processos de polimerização em suspensão são apropriados para obtenção de produtos para aplicações biotecnológicas e médicas, dentre outras. O objetivo principal deste trabalho é apresentar uma discussão dos aspectos fundamentais inerentes aos processos de polimerização em suspensão, visando a uma compreensão do efeito das principais variáveis de processo sobre o desempenho de polimerizações em suspensão. Mostra-se também que a espectroscopia do infravermelho próximo (NIRS) pode ser muito útil para permitir o monitoramento e o controle em tempo real de processos de polimerização em suspensão, para a obtenção de materiais poliméricos com características especiais. Palavras-chave: Polimerização, suspensão, espectroscopia, infravermelho próximo. A Review on Suspension Polymerization ProcessesAbstract: Several processes can be employed for manufacturing polymer materials. Each process presents some intrinsic features that lead to production of resins with peculiar properties, which define the end-use application of the final polymeric material. Suspension polymerization processes are extensively used because of their many advantages, such as the easy separation of the polymer particles, easy removal of the heat of reaction, easy temperature control and low levels of impurities and additives in the final polymer material. For this reason, suspension polymerization processes are suitable to produce polymer resins for biotechnological and medical applications. The main objective of this work is to discuss the fundamental aspects of suspension polymerization processes, focusing upon the effects of the main process variables on the performance of suspension polymerizations. Additionally, it is shown that near infrared spectroscopy (NIRS) can be useful for monitoring and real time control of suspension processes, allowing for production of polymer beads with controlled morphology.

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Section: Efeitos Gel E Vítreounclassified

Uma revisão sobre os processos de polimerização em suspensão

2007

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“…• The concentration of polymeric diradical species S n is three orders of magnitude smaller than the polymeric monoradicals P n and Q n [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. The diradical species S n could then be neglected [3,4,6,8,10] (Fig.…”

Section: Kinetic Modelingmentioning

confidence: 99%

“…So, in order to account for the gel effect, a diffusion model taken from the literature and then modified by Table 4 Measured and predicted average molecular weights in number, measured average molecular weights in mass and optimized initiator efficiency Rouge [13] is taken. The expression proposed by Chiu [1] (for the methyl methacrylate) is the following:…”

Section: Gel Effect and Kinetic Constantsmentioning

confidence: 99%

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Kinetic modeling of free radical polymerization of styrene initiated by the bifunctional initiator 2,5-dimethyl-2,5-bis(2-ethyl hexanoyl peroxy)hexane

Cavin

2000

Polymer

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This paper deals with the kinetic study of bulk free radical polymerization of styrene initiated with the commercial bifunctional initiator 2,5-dimethyl-2,5-bis(2-ethyl hexanoyl peroxy)hexane (Lupersol 256). The polymerization kinetics is investigated by DSC measurement for temperatures between 80 and 110ЊC and for initiator initial concentration from 0.115 up to 0.46 mol%. The experimental conversion and reaction rate are compared and discussed with the calculated values. For modeling the polymerization rate, a reaction scheme similar to the one given by Yoon and Choi (Polymer 1992;33(21):4582-4591) has been used and adapted. A detailed diffusional and semi-empirical model proposed by Chiu et al. (Macromolecules 1983;16(3):348-357) has been modified by Rouge (Etude de la polymérisation radicalaire du styrène initiée par un amorceur bifonctionnel dans un réacteur tubulaire à recyclage, Diploma work, DC, EPF, Lausanne, 1997) in order to describe these results. The model allows the description of the number molecular weight, but the polydispersity is underestimated for conversion higher than 70%. For temperature higher than 100ЊC, thermal initiation must be taken into account. The efficiency factor is found close to 1, but seems to decrease for temperatures above 100ЊC. ᭧

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“…Some of them are semi-empirical [1,8], others are based on parameters with clear physico-chemical meanings [2,7]. Several studies may be found in the literature on the comparison of different algorithms used for apparent rate constant calculation.…”

Section: Introductionmentioning

confidence: 99%

Comparison of two algorithms for calculation of the apparent rate constant in the kinetic modelling of diallyl terephthalate bulk polymerization

Hace¹

2005

E-Polymers

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Abstract:In the present study a comparison was made of two most frequently used algorithms for calculation of the apparent rate constant in the kinetic modelling of bulk cross-linking diallyl terephthalate (DAT) polymerization with four different peroxide initiators, bis(4-tert-butylcyclohexyl) peroxydicarbonate, dicyclohexyl peroxydicarbonate, benzoyl peroxide and dicumyl peroxide, in the temperature range from 50 to 150°C and at three different initiator loadings. The first algorithm is the CCS algorithm developed by Chiu, Carratt and Soong and the second is the S algorithm developed by Smoluchowski. Only two kinetic parameters had to be found by fitting a previously proposed kinetic model for bulk DAT polymerization, developed by Hace et al., to measured conversion points. Conversions and other necessary physico-chemical properties used for kinetic modelling were obtained from our previous kinetic studies on DAT polymerization.

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A computer model for the gel effect in free-radical polymerization

Abstract: In this paper the word enantioselective is always related to carbon 2 (enantiotopic) of the monomer, which becomes chiral after the insertion. The word diastereoselective is used with reference to the different reactivity of the diastereotopic faces of the monomer toward the insertion.

Cited by 263 publications

References 6 publications

Uma revisão sobre os processos de polimerização em suspensão

Uma revisão sobre os processos de polimerização em suspensão

Kinetic modeling of free radical polymerization of styrene initiated by the bifunctional initiator 2,5-dimethyl-2,5-bis(2-ethyl hexanoyl peroxy)hexane

Comparison of two algorithms for calculation of the apparent rate constant in the kinetic modelling of diallyl terephthalate bulk polymerization

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